1. Technical Field
This disclosure relates to a fixing liquid, a toner fixing method, a toner fixing device, an image forming method, and an image forming apparatus.
2. Description of the Related Art
An image forming apparatus such as a printer, a facsimile machine and a copying machine is an apparatus for forming an image containing a character or a symbol on a recording medium such as a paper medium, a cloth medium, and an OHP sheet, based on image information. In particular, an electrophotographic image forming apparatus has been widely used in an office since a high-resolution image can be formed on a normal paper sheet at a high speed. In such an electrophotographic image forming apparatus, a heat-fixing method has been widely used in which toner on a recording medium is heated and melted and the melted toner is pressurized so as to fix the toner on the recording medium. The heat-fixing method has been preferably used since a high fixation speed and a high fixed image quality, etc., can be provided.
However, an approximately half or more of an electric power consumed in such an electrophotographic image forming apparatus is consumed for heating toner in the heat-fixing method. On the other hand, a fixing device with a low electric power consumption (energy saving-type one) has been desired from the viewpoint of measures of environmental problems in recent years. That is, to extremely lower a temperature at which toner is heated to fix the toner, relative to conventional one, or a fixing method in which no heating of toner is required has been desired. Particularly, a non-heating fixing method of fixing a toner on a recording medium without heating the toner is ideal in terms of low electric power consumption.
As such a non-heating fixing method, for example, Japanese Patent No. 3290513 discloses a wet-type process for fixing toner wherein toner is dissolved or swelled by spraying or dipping an oil-in-water-type fixing agent capable of dissolving or swelling the toner onto the surface of a fixation medium on which unfixed toner is arranged at a predetermined position, in which agent an organic compound being insoluble or difficult to dissolve in water is dispersed and mixed in water, and subsequently, the fixation medium is dried.
However, when a large quantity of the fixing agent is applied onto an unfixed toner in the wet-type fixation process disclosed in Japanese Patent No. 3290513, a recording medium (a fixation medium) such as a transcription paper sheet absorbs a water content of the fixing agent so that cockle or curl is generated in the recording medium, since the oil-in-water-type fixing agent is used in which an organic compound being insoluble or difficult to dissolve in water is dispersed and mixed in water. Accordingly, stable and high-speed conveyance of the recording medium which is required for an image forming apparatus is significantly hindered. Then, when a large quantity of water contained in the fixing agent is evaporated by using a drying device so as to remove the water content from the fixing agent applied on the recording medium, an electric power is required which is comparable to an electric power consumed in an image forming apparatus for which a heat-fixing method is used.
Also, the surfaces of tone particles are commonly subjected to water-repellency treatment using a hydrophobic silica in order to prevent the toner particles from absorbing moisture in the atmosphere to aggregate to one another and maintain the fluidity of the toner. Therefore, when an aqueous fixing liquid containing water as a dispersive medium, such as a fixing agent as described above, is sprayed or dipped onto an unfixed toner on a recording medium, toner fluid particles subjected to a water repellency treatment are repelled by the aqueous fixing liquid. As a result, a blank portion is formed in a toner image and a defect is generated in the image.
FIGS. 1A, 1B and 1C are diagrams illustrating a fixing method of applying a water-based fixing liquid onto a toner subjected to water repellency treatment on a recording medium. As shown in FIG. 1A, a liquid drop of water-based fixing liquid 13 is dropped onto a layer of unfixed toner 12 subjected to water repellency treatment which has been transcribed on a recording paper sheet 11 as a recording medium by an appropriate fixing liquid applying device. Then, as shown in FIG. 1B, when the liquid drop of water-based fixing liquid 13 contacts the layer of unfixed toner 12 subjected to water repellency treatment, a particle of unfixed toner 12 subjected to water repellency treatment is repelled by the liquid drop of water-based fixing liquid 13. As a result, as shown in FIG. 1C, the particle of unfixed toner 12 subjected to water repellency treatment which has been repelled by the liquid drop of water-based fixing liquid 13 moves to the periphery of the water-based liquid drop 13, with the spreading of the water-based fixing liquid 13 on the recording paper sheet 11. Then, an undesirable blank portion in the toner subjected to water repellency treatment is formed on the layer of unfixed toner 12 subjected to water repellency treatment which has been transcribed on the recording paper sheet 11, whereby a defect is generated in a toner image. Thus, when the water-based fixing liquid 13 is used, there is a problem such that the layer of unfixed toner 12 which has been transcribed on the recording paper sheet 11 is readily disturbed.
Then, as a fixing liquid which repels no unfixed toner subjected to water repellency treatment, there is disclosed a non-aqueous fixing liquid in which a material for dissolving or swelling a toner is dissolved in a non-aqueous solvent. For example, Japanese Laid-Open Patent Application No. 2004-109749 discloses a fixing liquid in which an aliphatic dibasic acid ester, etc., as a component of a material for dissolving or swelling a resin component constituting a toner is diluted (or dissolved) with a non-volatile dimethylsilicone as a diluent (solvent). Also, for a solution for fixation which can be used for a fixing method capable of sharply and readily fixing an unfixed image formed by an electrostatic method on a image receiving sheet without disturbing the image, Japanese Laid-Open Patent Application No. 59-119364 discloses a mixed solution for fixing an image of unfixed toner which can dissolve the toner and be provided by admixing 8-120 parts by volume of a silicone oil into 100 parts by volume of a solvent having a miscibility to the silicone oil. Such a non-aqueous fixing liquid contains a non-aqueous solvent having a high affinity with an unfixed toner subjected to water repellency treatment and, therefore, can dissolve or swell a toner without repelling the unfixed toner subjected to water repellency treatment, so that the toner can be fixed on a recording medium.
Herein, the use of a VOC (volatile organic compound) as a non-aqueous solvent used for a non-aqueous fixing liquid is not preferable since it brings an adverse affect to a human body and generates unpleasant odor. Therefore, as a non-aqueous solvent used for a non-aqueous fixing liquid, in fact, a non-volatile non-aqueous solvent is used.
However, a non-aqueous fixing liquid in which a material for dissolving or swelling a toner is dissolved in a non-volatile non-aqueous solvent has a high permeability into a recording medium. Therefore, when a non-aqueous fixing liquid as described above is sprayed or dropped onto an unfixed toner on a recording medium, the non-aqueous fixing liquid diffuses on and penetrates through the recording medium with a high speed, and only a portion of the material for dissolving or swelling a toner which is contained in the non-aqueous fixing liquid dissolves or swells the unfixed toner on the recording medium. Then, the remaining portion of the material for dissolving or swelling a toner is not utilized for dissolving or swelling the toner but diffuses on or penetrates through the recording medium with the non-aqueous solvent. Thus, since only a portion of the material for dissolving or swelling a toner which is contained in the non-aqueous fixing liquid dissolves or swells an unfixed toner on a recording medium, it is necessary to increase the concentration of the material for dissolving or swelling a toner which is contained in the non-aqueous solvent. For example, the inventors have found that the concentration of a solvent dissolved in a silicone oil as a non-aqueous solvent is necessarily equal to or more than 20% by weight with respect to a solution for fixation disclosed in Japanese Laid-Open Patent Application No. 59-119364. Therefore, in regard to a non-aqueous fixing liquid in which a material for dissolving or swelling a toner is dissolved in a non-volatile non-aqueous solvent, the toner dissolving or swelling efficiency of the material for dissolving or swelling a toner is low.
FIGS. 2A, 2B, and 2C are diagrams illustrating a fixing method of applying a non-aqueous fixing liquid onto a toner subjected to water repellency treatment on a recording medium in which liquid a material for dissolving or swelling a toner is dissolved in a non-volatile non-aqueous solvent. As shown in FIG. 2A, a liquid drop of a non-aqueous fixing liquid 23 in which a material for dissolving or swelling a toner is dissolved in a non-volatile non-aqueous solvent is dropped onto a layer of unfixed toner 22 subjected to water repellency treatment which has been transcribed on a recording paper sheet 21 as a recording medium by an appropriate fixing liquid applying device. Then, as shown in FIG. 2B, the non-aqueous fixing liquid 23 described above which has contacted the recording paper sheet 21 has a high permeability into the recording paper sheet 21 and rapidly permeates into the recording paper sheet 21. As a result, as shown in FIG. 2C, a portion of the material for dissolving or swelling a toner which is contained in the non-aqueous fixing liquid 23 can dissolve or swell the unfixed toner 22 on the recording paper sheet 21, and, however, the remaining portion of the material for dissolving or swelling a toner does not dissolve or swell the unfixed toner 22 on the recording paper sheet 21 but penetrates through or diffuses on the recording paper sheet 21 with the non-volatile non-aqueous solvent. Thus, when a non-aqueous fixing liquid is used in which a material for dissolving or swelling a toner is dissolved in a non-volatile non-aqueous solvent, there is a problem such that the efficiency of utilizing the material for dissolving or swelling a toner is low.
Therefore, a fixing liquid may be desirable which is capable of fixing a toner on a recording medium more efficiently.
More specifically, it may be desirable to provide a fixing liquid, a toner fixing method, a toner fixing device, an image forming method, and an image forming apparatus, which are capable of fixing a toner on a recording medium more efficiently.